Utility model content
In view of the above drawbacks of the prior art, the technical problem to be solved by the utility model is to provide a kind of power supplys
Circuit is protected, the supply voltage and current conditions of DC back-up power supply can be read by hardware circuit, and distinguish by controller
Normal load or abnormal short-circuit conditions, and turned off output protection.
To achieve the above object, the utility model provides a kind of output protection circuit of DC power supply, including direct current
Source input terminal, voltage sampling circuit, current sampling resistor, amplifying circuit, controller, switching circuit and power protection output end；
The DC supply input is for connecting DC power supply, and the power protection output end is for connecting load；Institute
State the anode of DC supply input and positive direct-connected, the cathode of the DC supply input of the power protection output end
It is connected by current sampling resistor, switching circuit with the cathode of power protection output end；
The input terminal and DC supply input of the voltage sampling circuit are in parallel, are used for output voltage sampled signal；
The amplifying circuit is used to acquire the voltage differential signal at current sampling resistor both ends, and exports current sampling signal；
The controller for reading the voltage sampling signal and current sampling signal, and with the threshold value inside controller
It is compared, and then output switch control signal；
The switch control signal controls the cathode and the electricity of the DC supply input by the switching circuit
The connection and shutdown of the cathode of source protection output end；
The switching circuit includes pre-driver circuit and N channel MOS switch pipe, the source electrode and electricity of the MOS switch pipe
Sampling resistor connection is flowed, the drain of the MOS switch pipe is connected with the cathode of power protection output end, the switch control signal
It is connected by pre-driver circuit with the control electrode of MOS switch pipe；
The pre-driver circuit includes first resistor, second resistance, the 4th resistance, the 5th resistance, the 6th resistance, the 7th
Resistance, the 9th resistance, the tenth resistance, the first triode and the second triode, first triode and the second triode are NPN
Triode, the switch control signal are connected to the base stage of the first triode, the base of first triode by the 4th resistance
Pole is connected by the 9th resistance with the source electrode of MOS switch pipe, and the collector of the first triode passes through first resistor and power input
The anode connection at end, and by the connection of the base stage of the 5th resistance and the second triode, the base stage of the second triode passes through the 7th electricity
Resistance is connected with the source electrode of MOS switch pipe, and the collector of the second diode is connected by the anode of second resistance and power input
It connects；And connect with the control electrode of MOS switch pipe by the 6th resistance, the control electrode of the MOS switch pipe by the tenth resistance with
The source electrode of MOS switch pipe connects.
Further, the voltage sampling circuit is resistor voltage divider circuit, including first resistor and second resistance, described the
The anode connection of one end of one resistance and the DC supply input, one end of the second resistance and the DC power supply are defeated
Enter the cathode connection at end, the other end of the first resistor is connected with the other end of the second resistance, and output voltage samples
Further, the amplifying circuit includes amplifier, twelfth resistor, thirteenth resistor, the 14th resistance and
15 resistance, the amplifier include positive input terminal, negative input end and output end, the first end of the current sampling resistor and institute
The cathode connection of DC supply input is stated, and is connected by the 14th resistance with the negative input end of the amplifier；Electric current is adopted
The second end of sample resistance is connected by twelfth resistor with the positive input terminal of the amplifier；The output end of the amplifier passes through
15th resistance is connected with the negative input end of the amplification；The output end of the amplifier exports electric current by thirteenth resistor and adopts
Further, the amplifier is LM2904.
The utility model obtains the instant voltage value and instant electricity of DC power supply output by current sample and voltage sample
Flow valuve carries out shutdown protection by output protection circuit, keeps away when the threshold value of the current value and/or voltage value beyond setting
Exempt from DC power supply to damage because of short circuit for a long time.
To further illustrate each embodiment, the utility model is provided with attached drawing.These attached drawings are in the utility model discloses
A part of appearance mainly to illustrate embodiment, and can cooperate the associated description of specification former come the running for explaining embodiment
Reason.Cooperation refers to these contents, and those of ordinary skill in the art will be understood that other possible embodiments and sheet are practical new
The advantages of type.Component in figure is not necessarily to scale, and similar component symbol is conventionally used to indicate similar component.
Now in conjunction with the drawings and specific embodiments, the present invention will be further described.
As depicted in figs. 1 and 2, the utility model discloses a kind of output protection circuits of DC power supply, including direct current
Source input terminal 1, voltage sampling circuit 2, current sampling resistor 3, amplifying circuit 4, controller 5, switching circuit 6 and protection output connect
Mouth 7.VOUT+ and VOUT- is respectively the anode and cathode of DC supply input 1, and VO+, VO- are respectively DC power supply through exporting
The anode and cathode of protection output end after protecting circuit.VOUT+ and VO+ are direct-connected；VOUT- passes through current sampling resistor 2, switch
Circuit 6 and VO- electrical connection.
The first end of current sampling resistor 2 is connected with VOUT-, and the second end of current sampling resistor 2 is connected to switching circuit
6, the resistance value of current sampling resistor 2 is generally several milliohms to tens milliohms, according to will by electric current selected.
As shown in Fig. 2, amplifying circuit 4 includes amplifier U1, resistance R12, R13, R14, R15, the of current sampling resistor 2
Two ends are connected to the positive input terminal of amplifier U1 by resistance R12, and the negative input end of amplifier U1 is grounded by resistance R14, is put
The output end of big device U1 is connected to the negative input end of amplifier U1 by R15.The output end of amplifier U1 is defeated by resistance R13
Current sampling signal MCU-AD-IOUT out.In the present embodiment, amplifier U1 is technical grade two-path amplifier LM3904, tool
Body applies one of amplifier unit U1A, and the amplification factor A of amplifying circuit 4 is mainly determined by R15 and R14, can recognize
For amplification factor A=1+R15/R14.Specific amplifying circuit is chosen according to the actual needs of circuit, to guarantee that the electric current of output is adopted
The voltage of sample signal MCU-AD-IOUT is within the input range that controller 5 allows.
Controller 5 detects the voltage value of current sampling signal, when detecting that the corresponding current value of voltage value is greater than the set value
When, then overcurrent protection instruction is issued, signal MCU-IO1 is set as low level.Switching circuit 6 includes switching tube Q1, Q2 and Q3, is opened
It closes pipe Q1, Q2 and constitutes pre-driver circuit, driving switch pipe Q3 shutdown.Specifically, when signal MCU-IO1 is low level, Q1
Cut-off, Q2 conducting, Q3 cut-off, the circuit between VOUT- and VO- disconnect, and protect between the VO+ of output end and VO- without output electricity
Pressure, plays the role of output protection.When signal MCU-IO1 be high level when, Q1 conducting, Q2 cut-off, Q3 conducting, VOUT- and
Circuit communication between VO-, output voltage between VO+ and VO-.Switching tube Q1, Q2 provide pre-driver and level conversion effect,
So that switch tube Q3 carries out shutdown control when signal MCU-IO1 is low level.
In switching circuit 6, switching tube Q1 and Q2 form pre-driver circuit, are required according to circuit polarities, general to select
NPN triode, switching tube Q3 are protective switch, and operating current handling capacity and more than ten A- for meeting a few more than ten A of A- are up to a hundred
The impact resistance of the short circuit current of A, it is therefore desirable to select MOS switch pipe, parameter specification is answered depending on concrete application.
It is also defeated to DC power supply by voltage sampling circuit 2 while in order to distinguish the difference of overcurrent protection and short-circuit protection
The supply voltage for entering end 1 is acquired, and illustrative voltage sampling circuit 2 as shown in Figure 2 is bleeder circuit, including resistance
R3, R8, the VOUT+ of DC supply input 1 output voltage sampled signal MCU-AD-VOUT, voltage sampling signal after dividing
MCU-AD-VOUT is connected to the simulation input pin of controller 5, when the voltage value of MCU-AD-VOUT is under-voltage, drops into moment
Certain value, controller 5 are determined as short-circuit protection, at this time output signal MCU-IO1, and make signal MCU-IO1 low level, into
And on-off switching tube Q3 is to play the role of protection.If lacking under-voltage current foldback circuit, in external short circuit or overcurrent
In the case of, easily cause power supply damage.
In this embodiment, illustratively, switching tube Q1, Q2 MMBT2222, switching tube Q3 are metal-oxide-semiconductor
IRF2807, parameter are as follows:
Operating voltage (Vmax): 75V；
Internal resistance (RDS (ON)): 13m Ω；
Electric current (Imax): 82A；
Power consumption (Pmax): 200W.
The parameter of the devices such as remaining resistance, capacitor as shown in Fig. 2, be not described further herein.
In this embodiment, it is only limitted to that generally there are multiple simulation inputs to the specific requirement of controller 5, and quickly
The single-chip microcontroller of processing capacity can meet application requirement, such as common Kinetis KE02 series monolithic.Inside controller 5
The threshold value set to signal MCU-AD-VOUT and signal MCU-AD-IOUT and controller 5 carries out simple threshold values comparison, and carries out
Simple logic and/or can output signal MCU-IO1 switch tube Q3 carry out shutdown protection.After controller 5 can provide simultaneously
End processing, back-end processing include but not limited to carry out state instruction, carry out sound-light alarm or carry out remote alarms etc., these rear ends
Processing mode is the conventional treatment mode of conventional monitoring instruction class device, and explanation is no longer developed in details herein.
Although specifically showing and describing the utility model in conjunction with preferred embodiment, those skilled in the art is answered
This is understood, in the spirit and scope for not departing from the utility model defined by the appended claims, in form and details
On the utility model can be made a variety of changes, be the protection scope of the utility model.